SEATTLE — Amazon has agreed to a big expansion in Seattle less than a month after the e-commerce giant announced it was looking for a second headquarters in North America.

The Seattle Times reported the company confirmed Tuesday it has signed a lease for the entire office portion of a planned downtown skyscraper that will become the second-tallest building in the Pacific Northwest. The skyscraper will be among the company’s biggest office buildings when it opens in three years, with room for more than 3,500 additional employees.

Amazon will occupy about 722,000 square feet in the development, which is in the early stages of construction.

Last month the company said it will spend more than $5 billion to build another headquarters in North America to house as many as 50,000 employees outside its hometown of Seattle.